Native patchbay with customizable number of channels

[messmerd]

Hello, I'm working on adding support in LMMS for audio plugins with multiple audio channels. I'd like to allow LMMS's built-in Carla patchbay to support however many audio channels to/from LMMS that a user wants to expose, but Carla unfortunately only seems to support a fixed number of channels.

The C API provides carla_get_native_patchbay_plugin which creates a 2-input/2-output patchbay, and there are other similar functions that create a patchbay with a different fixed number of inputs and outputs, but I haven't found a way to create a patchbay with an arbitrary number of channels and be able to change that number afterwards.

In the source code, those C API functions are implemented in source/backend/engine/CarlaEngineNative.cpp. It appears that adding a new API function that creates a patchbay with a custom number of audio, midi, or CV channels would be a relatively simple task.

However, the ability to change the number of channels afterwards would be more difficult and I do not know enough about the codebase to say how feasible it would be.

Are there any plans to add this support?

[messmerd]

@falkTX Do you have any thoughts about this?

[falkTX]

dynamic IO is not really something I have interest in, another custom but static value is okay, fully dynamic not really

[messmerd]

That's okay. I may be able to offer a fixed set of input/output configurations in LMMS (i.e. 2x2, 3x2, 16x16), and just restart Carla in order to switch between them dynamically.